Rodent models of disease, especially genetically-modified mouse models, have provided powerful tools to investigate the processes underlying metabolic diseases, including obesity and Type 2 diabetes. In order to understand the physiology of such models and the alterations in metabolism that underlie their phenotypes, equipment capable of specialized and precise measurements must be employed to examine energy balance and metabolic variables. The Comprehensive Laboratory Animal Monitoring System (CLAMS) continuously and simultaneously monitors activity, feeding, and drinking, as well as VO2 and VCO2 for the determination of metabolic rate and RQ. Our Animal Phenotyping Core facility has a single 8-cage CLAMS that cannot keep pace with the high and accelerating demand for this service;this demand results from the increased number of investigators and mouse models that require this analysis. The current system is also inadequate for the analysis of animal models that employ multiple control groups. The purchase of a second, 12-cage system will permit the analysis of these animal models in a more timely fashion and the two systems together will enable the analysis of up to 20 animals at one time.